Mechanical furnace of the underfeed type



M. RATEL.

MECHANICAL FURNACE UF THE UNDERFEED- TYPE.

APPLICATION FILED MAB- 30, I914- I I Patented Jan. 18,1921.

PATENT OFFICE.

MAURICE RATEL, OF PARIS, FRANCE.

MECHANICAL FURNACE OETBIE UNDERFEED TYPE.

Specification of Letters latent.

Patented Jan. 18, 1921.

Original application filed March 28, 1913, Serial No. 757,353. Divided and this application flled March a0, 1914. Serial No. 828,423.

provide an improved device of this char acter.

Automatic stokers of the underfeed type heretofore employed have been more or less defective in their manner of distributing the fuel and cleaning the furnace. Where fixed plates or bars have been used for the rate, there is produced at the center a thic bed of burning fuel into which the air penetrates with difiiculty and wherein. the car bon dioxid produced in the neighborhood of the twyers is reduced to carbonmonoxid in passing through the incandescent fuel and, owing to the lack of sufficient air, escapes without combustion and with the consequent loss of heat. Furthermore, this type of furnace requires hand cleaning and therefore, imposes heavy labor on the fireman. To obviate the disadvantages of this type of furnace it has been suggested to effect distribution of the fuel and cleaning of the grate by movement of the bars in a variety of ways. Such movable grate bars, operating by shearing action on the fuel, are effective to a greater or less extent in breaking up and moving the body of incandescent fuel, but they are quickly burned out because surrounded on three of their faces with incandescent fuel for at least a part of the time.

To avoid the defects incident to this ty e of grate it has been suggested to effect ,t e feeding of the fuel and cleaning of the grate by inclining the grate so that the movement of the fuel and solid products of combustion is effected with the aid of gravity. In view of the relatively steep angle of repose possessed by the ordinary fuels, however, this type of grate requires considerable height whereby it is unavailable for use with locomotive or marine boilers or stationary boilers where a relatively high grate cannot be had.

It has also been suggested to provide an inclined grate with one or more fuel re torts or troughs which intersect the grate and to feed the fuelto the grate through said retorts or troughs by fuel feeding devices in each of them. Furnaces of this type heretofore constructed have not been entirely satisfactory, however, because with the available inclination of grate there has been a bad distribution of fuel and imperfect combustion arising from the uneven supply of air to the incandescent fuel. The angle of repose of the fuel being much greater than the angle of the grate, the fuel has had a tendency to collect in a thick bed at the upper part of the grate and,-the air peneand solid products of combustion in the nature of an avalanche, which carries with it both fuel and solid products of combustion onto the dumping sections of the grate. Much of this fuel is smothered in the ashes and'slag so that it is carried into the ash pit and becomes lost. Furthermore, when the fuel is fed at the same rate through the bottom of the retorts as at the top of the retorts, much fuel is ushed directly from the retorts onto the umping grate where it is buried in the ashesand slag, and becomes extin uished and lost.

. It is the o ject of the present invention to overcome these defects and disadvantages by providing a proper distribution of the fuel to the fuel bed and causing a continuous and re ular advancing movement of the entire uel bed by feeding successively decreasing quantities of fuel to the successive portions of the main grate as it inclines toward the dumping grate, as by use of fuel feeding devices of successively decreasing stroke, orby use of fuel feeding devices having the same stroke but of successively decreasing capacity, or by both.

A further object of the invention is to provide, in combination with fuel feeding devices of the type last referred to, a receiving grate at the foot of the incline of the main grate, said receiving-grate preferably comprising a plurality of movable grate bars,

the same desirably having movement in reverse directionsin the same plane, so that they will act like a Sifter-and insure a regular advancement of the fuel bed.

Another object of the invention is to provide a mechanical furnace as heretofore described wherein the bars of the receiving grate are provided with an air supply which diminishes in quantity toward the dumping grateand which in the rearmost bars may be replaced by an injection of steam to form combustible gases by coming in contact with the incandescent solid products of combustion.

Another object of the invention is to obviate the difficulties heretofore experienced from the rapid burning of the twyers by so constructing them that the air flowing through the same comes into cooling contact with the heated surfaces or that the ashes tend to form protective layers on their exterior surfaces, or both; or, in combination therewith, said twyers may be further cooled by the injection of steam, humid air, water spra or circulating water. Furthermore, to o viate the difficulty heretofore experienced from the rapid burning of the dumping grate, the same or a similar construction may be applied thereto.

A further object of the invention is to provide,'in combination with a mechanical furnace of the type heretofore described, means for varying the rate at which the fuel and air is supplied thereto, even though only a constant speed motor is available, said means preferably permitting of automatic variation and control.

Other objects relate to the provision of a mechanical furnace of the type referred to which is simple in construction, eflicient in operation, inexpensive to maintain, and economical in its use of fuel.

The invention is capable of receiving a variety of mechanical expressions, some of which are shown on the accompanying drawings, but it is to be expressly understood that the drawings are for purposes of illustration only and are not to be construed as a definition of the limits of the invention, reference being had to the appended claims for that, purpose.

In said drawings, Figure l is a vertical section through a trough or retort of a mechanical furnace employing an underfeed stoker which embodies the present invention.

plan view of the twyers of for varying the working of the furnace whena constant speed motor is employed; and

Fig. 8 is a Schematic View of means for individually varying the speed of each stoker and automatically controlling the admission of air.

The present invention is ca able of aplication to a wide variety 0 boilers and ibrms of furnaces and, therefore, as it is not limited to any particular type of boiler or furnace construction, the details of the latter have not been illustrated.

In the embodiment of the invention shown in Fig. 1, a construction of grate is employed which is particularly suitable for use with marine and locomotive boilers. The main grate is composed of a series of twyers 37 of any suitable construction successively decreasing in elevation from a medial fore and aft line toward the sides of the furnace so as to provide a grate of the gravity feed type, said twyers being separated by fuel retorts or troughs 34, 35, 36, etc., at and on both sides of said medial line. Said troughs or retorts are shown as of successively decreasing depth but they may be of the same or of successively decreasing cross section. The fuel is supplied the grate, from the hopper 81, in progressively decreasing quantities from said medial line toward the sides of the furnace by fuel feeding devices of progressively decreasing stroke or capacity in the successive retorts or troughs. The said fuel pushers may be of any suitable construction, being shown as of successively decreasing capacity toward the sides of the furnace and each com arising a main piston or pusher 82, actuate in any suitable way as by crank mechanism from the shaft 22, and a plurality of secondary pushers 83 connected thereto by the rod 86, the succeeding pushers in each trough also being of successively decreasing capacity from the front to the rear of the grate. Receiving grates composed of movable bars 38, 39, 40, etc.,-desirably having reverse movement in the same plane, are preferably positioned at each side of the furnace at the base of the inclines of the main grate, and said grate barsmay be provided with an air-supply progressively decreasing toward the dumping grate, as diagrammatically illustrated by the decreasing size of the air passages 84 in said bars. Air is supplied said twyers and bars in any suitable way. A dumping grate 41 is also shown at the outer side of each of said receiving grates.

The twyers are preferably so constructed that their surfaces are maintained relatively cool. To this end they may be provided with external grooves 42 in which the ashes collect to form a heat-protecting layer, as shown in Figs. 3 and 4; or they may be provided interiorly with partitions 31 for dioperative position.

. alternatin recting the incoming air into coolin contact withtheir surfaces, as-shown in 1g. 5; or they may be provided with said partitions 31 and have their Surfaces corru ated to form external recesses in which t e ashes collect to form a protective layer, as shown in Fig. 6. Said twyers may be of any suitable form and cross section and they may be built up in any suitable wa Any'suitable means may provided for driving the stoker and varying 1ts speed. In the form shown, shaft 22- is driven from shaft 19 through the belt or chain drive 20 and speed reducing mechanism of any suitable construction, said shaft 19 in turn being driven from any suitable source of power. When a steam engine or direct current motor is employed the speed may be varied automatically or otherwise in any suitable 'way,

as by automatically controlled valves or anautomatically controlled rheostat. When an current is used however, and particular y when a three hase current is employed so that only slig t variations of speed may be obtained by variation of the current, c ange speed devices of any suitable construction may be a lied to the fan and stokers and also indivr uall to each stoker to secure the proper regulation of the s eed. As diagrammatically illustrated in Fig. 7, the main shaft 19 may be driven from the drivlng shaft 43 of a constant speed motor 44 through suitable gearing 48. A clutch is diagrammatically illustrated at 45 and the fan or blower at 47 said fan and main shaft 19 being driven from the shaft 43, upon actuation of the clutch 45, through a change speed box 46 of, any suitable construction. In addition-to the mechanism just described for varying the speed of the entire stoker and blower, a chan e s eed box may be provided for each' in 1vi ual stoker as shown diagrammatically in Fig. 8, wherein 49 is the change speed box, 50 is a gear driven in any suitableway from the main, shaft 19,

and 51 is a clutch of any suitable construction for connecting the gear 50 with the driving shaft of the change speed mechanism in the box 49, said clutch being normally pressed into operative position by the spring 54. The change speed mechanism is shown ascontrolled by a lever 55 having a handle 56 which controls a catch for engagement with the teeth 58 of the sector plate 85. Said lever 56 may have an extension 57 for engagement with ,the arm 53 of the bell crank 52', 53, which in turn controls the movement of the clutch 51 into and out of It is also desirable that the mechanism for changing the speed of each stoker be connected to the damper for admitting air to the furnace so as to maintain a constant relation between the quantity of fuel and the quantity of air supplied to the furnace.

'55 by a cable 59, a counterweight 62 being shown as connected to the arm 61 of the damper to facilitate adjustment of the latter.

While the constructions shown on the drawings have been described with considerable particularity it is to be expressly understood that the invention is not limited thereto, as the same is capable of being embodied in a variety of forms. In lace of the types of fuel feeding devices s own, any other suitable fuel feeding means for feeding progressively decreasing quantities of fuel may be employed. The number, form and inclination of the twyers and the number and size of the fuel retorts or troughsmay also .or blower it is to be understood that it is within the contemplation of this invention to use a natural draft when such is available. Reference is therefore to be had to the claims hereto appended for a definition of the limits of the invention.

This application is a division of my application Sr. No. 757,353- filed March 28, 1913 and is directed more particularly to one embodiment of the generic invention, other embodiments and generic features of construction being claimed both generically and specificall in the original and other divisional app ications.

What is claimed is 4 1. In an automatic underfeed stoker a series of twyers successively decreasing in elevation from a medial foreand aft line toward the sides of the furnace, fuel retorts or troughs at and on both sides of said medial line and means for feeding fuel through said retorts or troughs to said twyers. a

2. In an automatic underfeed stoker, a series of twyers successively decreasing 1n elevation from a medial fore and aftline toward the sides of the furnace, fuel retorts or troughs at and on both sides of said medial line, and means for feeding progressively smaller quantities of fuel through the successive retorts or troughs on each side of or troughs at and on both sides ofsaid medial line, and a fuel pusher reciprocatory in each of said troughs or retorts for feed ing fuel through said retorts or troughs to said twyers.

- 4. In an automatic underfeed stoker, a series of twyers successively decreasing in elevation .froma medial foreand aft line .to-

the successive retorts or troughs on each.

side of said medial line.

5. In an automatic underfeed stoker, a

series of twyers successively decreasing in elevation from a medial fore and aft line to ward the sides of the furnace, fuel retorts or troughs at and-on both sides of-said medial line, and fuel feeding means in said retorts or troughs for feeding a progressively diminishing quantityof fuel along each retort or trough.

6. In an underfeed stoker, a plurality of twyers successively decreasing in elevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, and means for feeding fuel to said twyers at said intermediate line'and on both sides thereof.

7. In an underfeed stoker, a plurality of twyers successively decreasing in elevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, and means for feeding fuel to said twyers at said intermediate line and at a plurality of positions on the defl-ivitieson both sides of said intermediate 8. In an underfeed stoker, a plurality of twyers successively decreasing in elevation from an intermedlate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, fuel retorts or troughs at said intermediate line and of progressively decreasing cross section on each side of said intermediate line, and means for feeding fuel through said retorts or troughs.

9. In an underfeed stoker, a plurality of twyers successively decreasing in elevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, fuel retorts or troughs at and on each side of said intermediate line, and fuel feeding devices successively decreasing in capacity for feeding progressively smaller quantities of fuel through the successive retortsor troughs.

10. In an underfeed stoker, a plurality of twyers successively decreasing in elevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, fuel retorts or troughs at and on each side ofsaid intermediate line, and fuel feeding devices in the respective retorts or troughs operative to iced progressively smaller quantities of uel.

11. In an underfeed stoker, a plurality of twyers successively decreasing inelevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, means for feeding fuel to said twyers at and on each side of said intermediate line, and reciprocating grate bars on which the solid matter is delivered from the declivities of said twyers.

12. In anunderfeed stoker, a plurality of twyers successively decreasing in elevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, means for feeding fuel to said twyers at and on each side of said intermediate line, and'a grate, having a progressively decreasing air supply toward the side of the furnace, on which the solid matter is delivered from each declivity of the twyers.

13. In an. underfeed stoker, a plurality of twyers successively decreasing in elevation from anintermediate line toward. the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from anv intermediate portion toward the sides of the furnace, means for feeding fuel to said twyers at and on each side of said intermediate line, grate bars reciprocating transversely to the declivity of said twyers and on which the solid matter 15 delivered, and dumping grates at the outer sides of said gratebars.

14. In an underfeed stoker, a plurality of twyers successively decreasing in elevation from an intermediate line toward the sides .of the furnace whereby the fuel and solid twyers successively decreasing in elevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate portion toward the sides of the furnace, said twyers having ex ternal ash-collecting recesses, and means for feeding fuel to said twyers at and on each side of said intermediate line.

16. In an automatic underfeed stoker, a plurality of twyers successively decreasing in elevation from a medial line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from the center to the sides of the furnace, fuel retorts or troughs between said twyers, and fuel feeding devices in said retrots or troughs for feeding progressively smaller quantities of fuel through the successive retorts or troughs on each side of said medial line.

17. In an automatic underfeed stoker, a plurality of twyers successively decreasing in elevation from a medial line toward the sides of the furnace whereby. the fuel and solid products of combustion are fed by gravity from the center to the sides of the furnace, fuel retorts or troughs between said twyers, and fuel feeding devices in said retorts or troughs provided with fuel feeding members of successively decreasing capacity.

18. In an automatic underfeed stoker, a plurality of twyers successively decreasing in elevation from a medial line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from the center to the sides of the furnace, fuel retorts or troughs between said twyers, and fuel pushers in said retorts or troughs, each comprising a fuel feedlng ram and a member reciprocating therewith and having rojections of successively decreasing heig t.

12). In an automatic underfeed stoker, a series of fuel supporting surfaces constituting twyers successively decreasing in elevation from a medial fore and aft line toward the sides of the furnace, fuel retorts or troughs between said twyers at and 'on both sides of said medial line, and means for feeding fuel through said retorts or troughs to said twyers. V

i 20. In an underfeed stoker, a plurality of twyers successively decreasing in elevation from an intermediate line toward the sides of the furnace whereby the fuel and solid products of combustion are fed by gravity from an intermediate ortion toward the sides of the furnace, said twyers having a corrugated surface, and means for feeding fuel to said, twyers at and on each side of said intermediate line.

21. In an automatic underfeed stoker, a series of twyers providin fuel-supporting surfaces which are incline laterally on each side of an intermediate fore and aft line fuel retorts or troughs at each side of said fore'and aft line and substantially parallel thereto for discharging fuel to said surfaces along a plurality of lines spaced in the direction of inclination of said surfaces, and means for feeding fuel through said retorts or troughs to said fuel-supporting surfaces.

22. In an automatic underfeed stoker, a series of twyers providing fuel-supportin surfaces which are inclined laterally on eac side of an intermediate fore and aft line, fuel retorts or troughs between said twyers at each side of said fore and aft line and extending substantially parallel thereto, and means for feeding progressively smaller quantities of fuel through. the .retorts ortroughs which succeed each other in the di rection of decreasing elevation of said fuelsupporting surfaces.

23. In an automatic underfeed stoker, a series of twyers providing fuel-supporting surfaces which progressively differ in height on each side of an lntermediate fore and aft line, a pluralit of fuel retorts or troughs at each side 0 said fore and aft line and extending substantially parallel thereto, and means for feeding fuel through said retorts or troughs to said fuel-supporting surfaces, said fuel-feeding means being of progressively decreasing capacit in successive retorts or troughs in the irection of down Evard inclination of the fuel-supporting suraces.

In witness whereof'I have hereunto set my hand this 27th day of February, 191 1.

MAURICE RATEL. 

